Data communication systems exchange user data for user devices to provide various data communication services. The user devices may be phones, computers, media players, intelligent machines, and the like. The data communication services might be media streaming, video conferencing, machine-to-machine data transfers, internet access, or some other data communication service.
Data communication systems uses wireless access points to extend the range of their communication services and enable user service mobility. The wireless access points perform wireless networking tasks like device handovers, radio interference management, and multipoint coordination. To facilitate these wireless networking tasks, the wireless access points communicate over signaling links. In Long Term Evolution (LTE) networks, the wireless access points are evolved Node Bs (eNodeBs), and the signaling links between the eNodeBs are X2 signaling links.
LTE eNodeBs also offer a Device-to-Device (D2D) communication service. The D2D communication service enables User Equipment (UE) to perform direct wireless transmission/reception without user data traversal through the eNodeB. For the D2D service, the eNodeB schedules one UE to transmit over an LTE resource block, and the eNodeB also schedules other UEs to receive over that same LTE resource block. Thus, a UE transmits directly to other UEs over the same resource blocks. The eNodeB controls and schedules D2D communications between the UEs, but the eNodeB does not relay user data between the UEs for the D2D communication service.
LTE eNodeBs are available in varying form-factors and with differing networking capabilities. Large macrocell eNodeBs are coupled to LTE network cores and serve both UEs and smaller access points like picocell eNodeBs. In turn, the picocell eNodeBs serve both UEs and even smaller femtocell eNodeBs. The femtocell eNodeBs serve UEs and perhaps even tiny nanocell eNodeBs. Unfortunately, current wireless communication networks do not effectively integrate X2 and D2D systems. In particular, UE D2D communications in LTE networks do not effectively support X2 signaling in the femtocell/picocell wireless networking environment.